IR Filters remove the infrared light that is left over from the 808nm -> 532nm conversion process through the crystals. IR filters are important when taking into account the advertised power output of a laser, as a laser advertised at 100mw but has no IR filter could very well mean there is 40mW of IR and only 60mW of green light. Its mostly about getting what you paid for.

There are some people who will say that safety is an issue with no IR filter, the argument being that the diffuse reflections and high divergence of IR as it exists your laser can cause damage to your eyes because you cannot blink as you cannot see the IR light, which makes sense, but I have never seen any laser that outputs enough IR (Besides an IR laser :P) that is focused enough to pose any significant risk. It just diverges too quickly.

Helpful?

EDIT: GBD makes a good point about people looking into their laser and getting hit with IR, although ive never read any stories like that, its a good idea NOT to look into the end of any laser.

It all depends on the optics train inside the cavity, and the lenses used.

Different modules will have different cavity setups, for example, some modules do not have an expanding lens before the collimating lens.

Each design of module and/or cavity will be different. I have seen several green lasers (both modules and a lab-style unit) that have an IR beam profile remain extremely close to the green beam.

How are they rated? I.e., is there an OD rating, etc.? I did not see that specified...

Spyro, etc.: sorry to be a pest, but still looking for an answer here. Do the IR filters that are sold on the two sites above have an OD rating for 800-1100nm? If not ,how are they rated (i.e., 90% IR attenuation, etc.)?

I am ignorant here, and just want to know what I'd be buying.

I think I'd want the 10x10 panel all things being the same. However, if there were larger ones, that would help in arranging them for testing as opposed to inserting for permanent blockage ...

man, all this is confusing. basically an ir filter is just to make your laser light seem brighter to the eye?

Nah. Let's say you purchase a 100mW green laser. The laser arrives at your house. You look at it and realize it does not have an IR filter. Once you install the IR filter, the power drops down to 60mW. This means that 60mW of the light is green light, and the other 40mW is IR light. In essence, you didn't get what you paid for because you only received a laser that emits 60mW of green light, not 100mW.